The pattern of early post-fertilization development is under the control of regulatory components whicc are built into the egg cytoplasm during oogenesis. Those regulatory components are, therefore, of maternal origin. Mutations which alter those gene products give rise to "maternal effects". In one species of amphibian - the Mexican axolotl (Ambystoma Mexicanum) - several such maternal effect mutations have been recognized. By analyzing eggs and embryos which are spawned by females which are homozygous for any of the maternal effect genes it should be possible to gain substantial insight into the manner in which the egg cytoplasm regulates gene expression during early embryogenesis. This proposal is presently investigating several aspects of the molecular biology of gene action during the period between fertilization and gastrulation. These aspects include RNA synthesis, protein synthesis, and cell-surface ccmponents. Once these phenomena are adequately described in normal embryos, comparative studies will be carried ouw with mutant embryos.